1. Field of the Invention
This invention relates to a process for the manufacture of flame-retardant polystyrene foams in which a stabilizer of a dialkyl-tin carboxylate or a mixture of a dialkyl-tin carboxylate and a barium and/or cadmium carboxylate is added to the extrusion mixture.
2. Description of the Prior Art
Flame-retardant polystyrene foams are produced by a well known method of melting the plastic material in an extruder, mixing it with a volatile blowing agent, extruding the mixture into the surrounding atmosphere and cooling the foam. By adding organic halogen compounds, such foams are usually self-extinguishing. Most of the halogen compounds tend to decompose at temperatures above 200.degree. C. If the extrusion temperature, which is normally 180.degree. C. to 200.degree. C., is to be raised so that the throughput of the extruder can be increased, discoloration and thermal dosage of the foam from the decomposition products of the flame retardant may result.